Herpes-spreading monkey population growing in Florida
SILVER SPRINGS — The forest explodes with angry shrieks, grunts and squeals as monkeys fight near the banks of the Silver River, defending their space in an increasingly crowded habitat not their own.
The growing number of monkeys is something Steve Johnson worries about, as it raises the possibility of confrontations with humans and the expansion of the non-native primates’ range beyond the idyllic river in Marion County.
Johnson, a University of Florida professor of wildlife ecology and conservation, co-authored a recent study that estimated the monkey population on the Silver River will double by 2022.
That could mean somewhere near 400 monkeys prowling the marshy banks of the river.
“Unless there is some management action by the state to curtail their numbers, it’s going to create a situation where they will be forced to take more drastic action due to a serious incident,” Johnson said.
An estimated 176 monkeys lived on the Silver River in 2015, according to the UF study, which was led by Jane Anderson.
The study, which appeared in the Journal of Wildlife Management in 2019, detailed the state’s history managing the monkeys.
From 1984 to 2012, about 1,000 monkeys were removed or sterilized through permits issued by the state. But since 2012, the Department of Environmental Protection stopped issuing removal permits after a wave of criticism hit the agency when it became known that trapped monkeys wound up at research facilities.
It was about the same time that the DEP’s Florida Park Service took full control of Silver Springs from private operators. For decades, the Silver River’s headwaters were part of a theme park attraction.
Since then, the monkeys have continued to reproduce unchecked. The only state action came from the Florida Fish and Wildlife Conservation Commission, which in 2018 prohibited the feeding of wild monkeys.
Neither of the agencies immediately responded to phone and email messages for this story.
On the River
Chugging slowly down the Silver River, nature quickly envelopes.
Through the clear water, the white, sandy circles of spawning beds stand out like polka dots among the thick mats of green eelgrass that grow on the bottom.
Sun-basking turtles crowd logs, sometimes sharing space with an alligator. Herons and egrets carefully stalk the banks. Ducks float along, nibbling here and there. And cormorants sit in the trees, wings spread, drying their feathers before plunging back into the water after another fish. On special days, a manatee might slowly paddle by.
“This is the best office in the world,” said Capt. Nick Bozman, who runs tourists from around the globe up and down the river for three-hour tours of Florida’s best.
The serenity of the place is inescapable.
“It’s beautiful. It’s beyond beautiful. It will reset your brain. Even if there were no monkeys, people would still come. There aren’t many places like it. But if they see the monkeys, it’s like a bonus,” said Capt. Nick, who’s been piloting the waters of the Silver River for the past 20 years and who took Star-Banner journalists on a tour last week.
Over the years, he has noticed the monkey population increase.
“I’ve seen six different troops around here in one day,” Capt. Nick said. “The population, I’m pretty sure, is growing. There are so many of them that you never see. We see them 80 to 90% of the time. But sometimes I break my neck looking for them, and they are nowhere to be found.”
A small flotilla of kayaks mass near the bank. Cellphones go up, fingers point and smiles punctuate the oohs and aahs of the kayakers.
“Looks like we’ve got monkeys,” said Capt. Nick.
On a log, under the shade of palm fronds, a mother clutched her baby as it nursed. Not far away, a group of youngsters frolicked in the trees, chasing one another.
Further down the river, more monkeys sat along the bank, seemingly contemplating the river and the passing boaters.
As kayaks approach the bank, some monkeys move closer.
“They lose their timidness when they get fed,” said Capt. Nick. “I’ve seen them jump on boats.”
While illegal to feed the monkeys, the two signs warning against the practice at each end of the river do little to stop some.
“I see them (feeding the monkeys) all the time. I used to tell them not to, but people get so mad at you,” he said.
It’s dangerous for both humans and monkeys.
“I remember one time, somebody threw a piece of bread out there, and a baby grabbed it and ran up a tree. The male ran up the tree behind him, shoved the baby off the tree, and when he hit the ground, he must have hit a log because he didn’t move,” he said.
Some of the seemingly curious monkeys crawled out onto overhanging branches, shook those branches, and bared teeth while staring at the boaters.
“That was aggressive behavior. They were warning them to leave,” Capt. Nick said, adding that sometimes the monkeys will squirt urine or defecate.
Before long, the area was thick with as many as 50 monkeys on both banks. Then something popped off.
In the underbrush, just off the bank, palm fronds shook violently, shrieks drowned out the soothing babble of the river’s water. Flashes of brown and white fur and pink flesh streaked through the forest crashing through the vegetation. The once contemplative monkeys on the banks scattered deeper into the bush.
Then it was quiet again.
“Even within the same troop, they have their own space. They are very territorial,” Johnson said. “That can become more of an issue if the population continues to grow.”
Know your monkey
The monkeys of the Silver River are rhesus macaques.Their native territory extends from parts of Afghanistan, Pakistan, India, Southeast Asia and into China. But they are easily adaptable and do well in captivity, which made them popular as research animals and for entertainment at roadside attractions.
It was their popularity as attractions that brought them to Silver Springs almost 90 years ago. Colonel Tooey — Colonel was his first name, not a rank — operated a jungle cruise boat on the river in the 1930s.
Tooey wanted to jungle-up his cruises, so he bought six rhesus macaques to Ocala. He let them loose on a small island on the river, still known as Monkey Island, and almost as soon as they were on dry land, the monkeys swam away.
That small troop found a cornucopia of tasty plants, insects and bird eggs. Enough to prosper and multiply.
Monkey troops include related females and males, not always related. Males come and go either on their own or by force.
Once on their own, males try to join other troops. They can travel miles in search of a troop. Females run the groups and usually stick around for life.
That’s why Johnson can’t help but shake his head when he reads some of the screaming headlines after a Silver River monkey pops up in an unfamiliar place.
“They're here! Invasive, herpes-carrying monkeys reach the First Coast,” a Jacksonville news headline blared recently after several sightings of a rhesus macaque.
In the past, monkeys have popped up in Hillsborough, Orange, Flagler, Duval, Putman and other counties.
Johnson credits these sightings to wandering males.
“Males that get kicked out or strike out on their own, in their native range, could challenge for dominance or get taken in by another group. So he’s searching,” Johnson said.
But there are no monkey troops in Jacksonville, or Tampa, or Apopka. Wandering males can be aggressive, but the sightings are no cause for panic, he said.
For Johnson, it’s the females that do leave and form new troops that are more troubling.
From six individual monkeys, five established troops emerged. And they are expanding. One small troop lives on the nearby Ocklawaha River.
“As the population continues to grow, the instance of solitary males and the chance of new troops forming on the Ocklawaha will continue,” he said.
At what price paradise?
As the monkey population continues to grow unabated, people like Johnson worry about the impact on the native plants and animals.
About a decade ago, Johnson started a study to see what effect the monkeys were having on the structure of the forest. The study involved trapping a few monkeys and outfitting them with tracking collars.
“I guess one of the rivets on the collar caused an abrasion, and a boat captain took a photo of it and posted it on Facebook,” Johnson said.
He said the reaction from the public was loud and angry. The state pulled the plug on the study, and since then, only observation is allowed.
On the river, monkeys like to eat the tender shoots that grow on the tips of branches. They break off the tip, eat a few shoots, drop the rest in the river and break off another branch, and then another.
More monkeys also mean more chances of conflict with people. Not long ago, the state temporarily closed portions of the park due to aggressive monkeys, including one incident where a monkey chased a family.
Besides attacks on humans, which the FWC stopped tracking decades ago, about a quarter of the monkeys carry the herpes B virus.
Johnson said the chances of a monkey infecting a human are slim, but they are not zero. The only verified transmissions of herpes B from monkeys to humans came in lab settings. The last fatal infection was in 1997, with 21 fatalities listed since 1932, according to the Centers for Disease Control and Prevention.
“I understand why they don’t want to address the issue. It’s a lose-lose situation. But if they do nothing, they are potentially opening up a barrel of monkeys, so to speak,” Johnson said. “It’s not an issue if it’s catching pythons. No one cares about snakes. When it’s a furry, charismatic animal, it makes it different.”
For Capt. Nick, the monkeys help make him money, but his love for the Silver River creates a philosophical struggle he hasn’t been able to resolve, either.
“First thing everyone asks about is the monkeys. They are good for my business,” he said. “But a lot of times, you can see the harm they are doing to the environment. They are not supposed to be here. It’s a double-edged sword.”
Contact Carlos E. Medina at 867-4157 or email@example.com